JPH1199480A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polishing pad which has satisfactory hardness and wet strength and by which clogging is eliminated by specifying the hardness of the polishing pad surface formed by a non-woven fabric formed by non-heat fused fiber impregnated with high molecular elastic polymer. SOLUTION: A non-woven fabric for forming a polishing pad is formed by a non-heat fused fiber, and the hardness (JIS K6301 A type) of the polishing pad surface is set from 85 deg. to 99 deg. both inclusive. The apparent density of the non-woven fabric is preferably from 0.2 to 0.5 both inclusive. If the apparent density of the non-woven fabric is smaller than 0.2, the hardness of the obtained non-woven fabric becomes low. If it is larger than 0.5, the obtained non-woven fabric is of so close texture that the liquid permeability is deteriorated and retention and liquid discharge of slurry is deteriorated. The obtained non-woven fabric is impregnated with high molecular elastic polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing pad for precision polishing for a semiconductor wafer, a liquid crystal glass, a hard disk or the like. More specifically, the present invention relates to a polishing pad for chemical mechanical polishing (hereinafter, referred to as “CMP”) used in a multilayer wiring forming step in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art There have been several proposals for polishing pads for precision polishing. For example, JP-A-2-232
JP-A-173-173 and JP-A-4-115875 describe polishing pads made of polyurethane foam as polishing pads for semiconductor wafers and flat glass products, respectively. The general required characteristics of the polishing pad include high polishing speed, stability of polishing performance, in-plane uniformity as polishing accuracy, and the like. In the case of a polishing pad for CMP, in particular, a global region in the surface. Is important. In order to satisfy the step flatness, it is necessary to harden the pad. Therefore, as a polishing pad for CMP of an oxide film, a polishing pad made of a foamed sheet of a hard polyurethane resin has conventionally been used. . However, if the polishing pad is polished for a long time, the polishing agent or polishing debris used for polishing is clogged in the holes of the closed cells on the surface of the polishing pad. There was an inconvenience that the surface had to be dressed with diamond or the like. In this application, a polishing pad obtained by impregnating a synthetic resin into a nonwoven fabric made of rayon is also used.However, since the polishing pad has a low wet strength, it cannot be used for a long time. And the hardness was low, and the flatness of the semiconductor wafer could not be sufficiently satisfied. On the other hand,
Japanese Patent No. 59157 describes a polishing pad obtained by heat shrink-hardening a nonwoven fabric made of an aromatic polyamide fiber. However, the polishing pad has a hardness (JIS K
6301 A type) of 82 °, which was insufficient to satisfy the flatness of the semiconductor wafer.

[0003]

Accordingly, the present inventors have developed a polishing pad for precision polishing such as a semiconductor wafer, a liquid crystal glass, and a hard disk, particularly a polishing pad for CMP, which has sufficient hardness and wet strength. In addition, the results of intensive studies aimed at providing a polishing pad that can eliminate clogging with only a simple dressing such as bristle brushing without performing dressing that performs grinding using a diamond whetstone The present invention has been found, and an excellent polishing pad for precision polishing, particularly for CMP has been completed.

[0004]

That is, the present invention relates to a polishing pad comprising a nonwoven fabric made of non-heat-fused fibers impregnated with a high-molecular elastic polymer, wherein the polishing pad surface has a hardness of 85 ° or more. A polishing pad characterized by being at most 99 °.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The nonwoven fabric constituting the polishing pad of the present invention is not particularly limited as long as it is made of non-heat-fused fibers.
Hardness of the obtained polishing pad (JIS K6301A)
Mold) from 85 ° to 99 °, preferably from 88 ° to 9 °
Since it must be 8 ° or less, and because the polishing slurry needs to have chemical resistance to withstand strong acids and strong alkalis, it is desirable that the polishing slurry be made of synthetic fibers, and it is preferable that the polishing slurry be a high-density nonwoven fabric. . Here, the synthetic fiber component used is not particularly limited as long as it is a fiber-forming resin, and examples thereof include polyester, polyamide, and polyolefin.

Examples of the non-heat-fused fibers include polyester fibers, polyamide fibers, polyurethane fibers and the like, and it is preferable to use polyester fibers. Also,
It is preferable to use a heat-shrinkable fiber as the non-heat-fused fiber in order to adjust the density and hardness of the nonwoven fabric.
Here, the heat-shrinkable fiber used is preferably a fiber that shrinks by 30% or more and 90% or less in hot water at 70 ° C., and particularly preferably a fiber that shrinks by 35% or more and 70% or less. Further, when polyester fibers are used, it is preferable to increase the water absorption rate by performing a hydrophilic treatment in order to improve the compatibility with the abrasive slurry. This non-heat-fused fiber can be used by mixing not only one kind but also many kinds of non-heat-fused fibers.

As a method for producing a nonwoven fabric from the above fibers, a conventionally known method such as a needle punch method, a spun bond method, a spun lace method, a chemical bond method and the like are used. For example, in order to produce a non-woven fabric made of the above-mentioned non-heat-fused fibers, short fibers obtained by cutting the fibers into an appropriate length are mixed, cotton-spun using a roller card, flat card, or the like, and spun. The fibers are laminated mechanically or using an air stream. Thereafter, punching is performed with a needle with a barb using a needle rocker or the like, or entanglement treatment is performed using a high-pressure water stream to obtain a nonwoven fabric. The apparent density of such nonwoven fabric is
It is preferably 0.2 or more and 0.5 or less, and 0.25 or less.
It is particularly preferable that the ratio be not less than 0.4 and not more than 0.4. When the apparent density of the nonwoven fabric is smaller than 0.2, the hardness of the obtained nonwoven fabric is low, and when it is larger than 0.5, the obtained nonwoven fabric is too clogged to deteriorate the liquid permeability and retains or discharges the slurry. Gets worse. Here, the apparent density is calculated by dividing the basis weight (weight per unit area) of the nonwoven fabric by the thickness.

The obtained nonwoven fabric is impregnated with a polymer elastic polymer (hereinafter, the nonwoven fabric impregnated with the polymer elastic polymer is referred to as “base material”). Here, the polymer elastic polymer used is not particularly limited. For example, polyurethane resin, polyester elastomer resin, polyurea resin, polyurethane polyurea resin, polyacrylic acid resin, acrylonitrile-butadiene resin, styrene-butadiene resin, etc. Among them, a polyurethane resin such as a polyurethane resin, a polyurea polyurea resin, or a polyurethane / polyurea resin is preferable, and a polyurethane resin is particularly preferable. The type of the polyurethane resin is not particularly limited, and specific examples thereof include an ester type, an ether type, an ester ether type, and an ether carbonate type. These polyurethane-based resins include one or more polymer glycols selected from polyether glycol, polyester glycol, polyester ether glycol, polycaprolactone glycol, polycarbonate glycol and the like having an average molecular weight of 500 to 4000, and 4,4 ′. -Diphenylmethane diisocyanate, xylylene resin isocyanate,
Organic diisocyanates such as triresin isocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate, low-molecular-weight glycols, diamines,
It is obtained by reacting with a chain extender selected from hydrazine or a hydrazine derivative such as an organic acid hydrazide or an amino acid hydrazide.

Here, the resin used is preferably a linear resin, and the resin used has a 100% modulus of 200 kgf / cm ² or more and 500 kgf / c.
More preferably, it is not more than m ² . Especially 210k
It is particularly preferable that it is not less than gf / cm ^{2 and not} more than 400 kgf / cm ² . By using a resin having a high 100% modulus, the hardness of the surface of the polishing pad obtained by using the substrate can be increased.

In order to impregnate the high-molecular elastic polymer into the non-woven fabric, the non-woven fabric is usually impregnated with the high-molecular elastic polymer in the form of an organic solvent solution or dispersion (including an aqueous emulsion). Here, as the solution containing the solvent of the polymer elastic polymer, a solution composed of a good solvent of the polymer elastic polymer such as dimethylformamide, diethylformamide, dimethylacetamide, or tetrahydrofuran, or water in a poor solvent such as methyl ethyl ketone is used. A dispersion solution in which the polymer is dispersed, a solution in which a high-molecular elastic polymer is further mixed, or the like is preferably used. Since the solution containing the solvent for the polymer elastic polymer needs to dissolve or swell a part of the polymer elastic polymer, the solvent for the polymer elastic polymer is at least 50% or more.
Preferably, the content is 60% or more. The concentration of the polymer elastic polymer to be impregnated is preferably from 0.1 to 40%, from the viewpoint of the viscosity of the solution, and is preferably from 1 to 30%.
Is particularly preferred. If the concentration is lower than 0.1%,
The amount of the polymer elastic polymer fixed to the nonwoven fabric is reduced, and it becomes difficult to obtain the required hardness. On the other hand, when the concentration is higher than 40%, there is a disadvantage that the solution viscosity of the high-molecular elastic polymer becomes too high and impregnation of the nonwoven fabric cannot be performed. The polymer elastic polymer to be impregnated is 5% based on the weight of the nonwoven fabric.
It is preferable to select in the range of 100%. If this ratio is less than 5%, the resin will thinly or only partially adhere to the entanglement point and the outer peripheral portion of the fiber, and the hardness of the polishing pad finally obtained will be low. Also, 100
%, The structure of the base material becomes too dense, and when used as a polishing pad because the pores are filled too much, the flow of free fine particles and polishing dust is hindered and clogging is likely to occur.

The obtained substrate is dried at 40.degree.
Performed at 50 ° C. for 1 minute to 60 minutes under an air or nitrogen atmosphere. When the drying conditions are not satisfied, the high molecular elastic polymer impregnated in the nonwoven fabric moves to the lower layer side of the nonwoven fabric and is localized,
The solvent used shifts to a direction where evaporation of the solvent is intense, and uniform impregnation of the high-molecular elastic polymer into the nonwoven fabric is prevented.

It is preferable to impart hydrophilicity to the obtained substrate. The CMP is performed in a state of being wet with water because a polishing slurry is used, and it is preferable to increase the water absorption rate of the substrate in order to improve the familiarity between the substrate and the polishing slurry.
Here, in order to increase the water absorption rate of the substrate, the substrate to be used is subjected to a hydrophilic treatment. As the hydrophilic treatment agent to be used, for example, a nonionic material that does not contaminate the wafer to be polished is used. Is mentioned. Specifically, alkyl and allyl polyoxyethylene ethers, alkyl allyl formaldehyde condensed polyoxyethylene ethers, polyoxyethylene polyoxypropyl alkyl ethers, and polyoxyethylene ethers of glycerin esters
Preferred are ter, polyethylene glycol fatty acid esters, and dimethylpolysiloxane-polyoxyalkylene copolymers. As a method of applying the treatment to the substrate, for example, a method of impregnating the substrate with a hydrophilic treatment agent and then squeezing with a nip roll, or a method of applying the hydrophilic treatment agent to the substrate with a mesh roll is preferably used. .
The water absorption rate of the impregnated substrate after performing the treatment is preferably 1 to 60 seconds, and more preferably 15 to 40 seconds when the polishing slurry is dropped on the pad surface by 1 milliliter. Is particularly preferred. In a general polishing step, polishing is started within about 1 minute after the polishing slurry is started to flow on the pad. Therefore, the absorption time is preferably as fast as possible. The treatment for imparting hydrophilicity may be performed in a non-woven fabric state.

Furthermore, the substrate of the present invention preferably has excellent wet strength in order to withstand long-term use in a wet state. In the present invention, the polymer solution is mesh-rolled for the purpose of improving the slip with the roll on the surface of the nonwoven fabric or improving the surface smoothness of the polishing pad.
It may be applied with a tool or the like.

According to the present invention, a polishing pad is obtained by performing post-processing such as lamination of an adhesive tape on the back surface or cutting into a predetermined disk size using the above-mentioned base material. Here, the hardness (JIS K6301 A type) of the obtained polishing pad surface is 8
5 ° or more and 99 ° or less, preferably 88 ° or more and 98 ° or less. In addition, the polishing pad, during the manufacturing process,
For example, at the stage of the fiber constituting the nonwoven fabric, or at the stage of manufacturing the nonwoven fabric, the hydrophilic treatment is performed, and the water absorption rate of the obtained polishing pad is preferably set to 1 second / ml to 60 seconds / ml, It is particularly preferred to be 15 seconds / ml to 40 seconds / ml.

The polishing pad may be further subjected to punching (drilling) and grooving (grooving) on the pad surface as necessary.
Secondary processing such as processing may be performed.

Although the polishing pad alone can achieve a sufficient polishing rate by itself, it has been disclosed in Japanese Patent Application Laid-Open Nos. 6-21028 and 6-77185 in order to achieve a higher polishing rate. As described, the polishing pad may be made by laminating an elastic layer below the substrate.
By laminating the elastic layer, the polishing pressure transmitted to the polishing pad is vertically and equally transmitted within the pressure contact surface through the polishing object and the polishing liquid film, and the pressure deformation of the polishing pad itself is minimized, and It is preferable to achieve a high polishing rate and accurate in-plane uniformity and prevent the wafer from sagging and bordering, since it can be uniformly generated. As the elastic layer used here, a urethane foam material, a nonwoven fabric, a nonwoven fabric impregnated with urethane, or the like is preferably used.

[0017]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples. In the examples, the following values were determined by the following measurement methods. (1) Apparent density of nonwoven fabric The basis weight (weight per unit area) of the nonwoven fabric was calculated by dividing the thickness. (2) Hardness of polishing pad A spring-type hardness test was performed in accordance with JIS K-6301 except that measurement was performed using one polishing pad using a type A spring test. (3) Wet strength After immersing the prepared sample in tap water for 1 minute, JIS
The tensile strength was measured according to K-6550. (4) Water Absorption Rate The water absorption time when 1 ml of water was dropped on the surface of the polishing pad was measured.

Example 1 Non-heat-fused fiber 290 polyethylene terephthalate having an intrinsic viscosity of 0.6
The undrawn yarn obtained by melt-spinning at a temperature of 63 ° C. was drawn 2.3 times in a hot water solution of 63 ° C., and then crimped by a press-type crimping machine, and an oil agent was applied. The obtained fiber had a single yarn fineness of 2.0 denier. The fiber was cut into a fiber length of 51 mm. When the obtained fiber was immersed in a 70 ° C. warm water bath for 2 minutes, the shrinkage was 50%. This fiber is referred to as fiber A.

Similarly, an undrawn yarn obtained by melt-spinning polyethylene terephthalate having an intrinsic viscosity of 0.6 at 290 ° C. is drawn 3.0 times in hot water at 63 ° C.
After tension heat treatment at 0 ° C. and crimping by a press-type crimping machine, an oil agent was applied. The obtained fiber had a single yarn fineness of 1.9 denier. The fiber was cut into a fiber length of 51 mm. The obtained fiber was immersed in a 70 ° C. warm water bath for 2 minutes, but did not shrink at all. This fiber is referred to as fiber B.

Production of Nonwoven Fabric The above-mentioned fiber A and fiber B were mixed at a weight ratio of 67/33, applied to a roller card, formed into a web, and placed in a needle locker room equipped with a needle having 9 kick-up barbs. Punching was performed at a number of shots per cm ² . Subsequently, it was immersed in hot water of 69 ° C. for 1 minute,
Was heated for 2 minutes to obtain a dense nonwoven fabric having a basis weight of 400 g / m ² and an apparent density of 0.30.

Impregnation of high-molecular elastic polymer The obtained nonwoven fabric was impregnated with 100 parts of a 20% by weight 100% polyurethane resin solution having a modulus of 260 kgf / cm ^{2 and} 0.5 parts of polyethylene glycol-modified polysilicon oil. . The nonwoven fabric is pressed at a pressure of 3 kgf / cm ²
, Squeezed through a nip roll, and then allowed to dry in a hot air drier at 100 ° C. for 10 minutes to obtain a substrate. The weight ratio of the resin to the fiber in the obtained base material was 4
It was 0%.

Production of polishing pad A double-sided pressure-sensitive adhesive tape was laminated on the back surface of the obtained base material to obtain a polishing pad. The hardness of the surface was 96 °, the water absorption rate was 34 seconds / ml, and the wet strength was 21.4 kg / cm. When the semiconductor wafer was subjected to CMP using the polishing pad, the polishing rate was 2.5 times that of the conventional polishing pad made of foamed hard polyurethane. Also, dressing to grind the polishing pad surface with diamond is unnecessary,
Stable polishing could be continued only by brushing with nylon bristle yarn. Furthermore, the polishing flatness of the semiconductor wafer to be polished was good, and the life of the polishing pad was sufficient.

Example 2 The nonwoven fabric obtained in Example 1 was impregnated with a 1.0% by weight aqueous solution of polyethylene glycol-modified polysilicon oil for 1 minute, dried, and then dried.
100 parts by weight of a 100% polyurethane resin solution having a modulus of 300 kgf / cm ² was impregnated with 100 parts. The nonwoven fabric was squeezed through a nip roll having a pressure of 3 kgf / cm ² , and then left to dry in a hot air drier at 100 ° C. for 10 minutes to obtain a substrate. The weight ratio of the resin to the fibers in the obtained base material was 35%.

Production of polishing pad A double-sided pressure-sensitive adhesive tape was laminated on the back surface of the obtained base material to obtain a polishing pad. The hardness of the surface was 97 °, the water absorption rate was 30 seconds / ml, and the wet strength was 20.4 kg / cm. When a semiconductor wafer was subjected to CMP using the polishing pad, the polishing rate was 2.3 times that of a conventional polishing pad made of foamed hard polyurethane. Also, dressing to grind the polishing pad surface with diamond is unnecessary,
Stable polishing could be continued only by brushing with nylon bristle yarn. Furthermore, the polishing flatness of the semiconductor wafer to be polished was good, and the life of the polishing pad was sufficient.

Comparative Example 1 Using the same non-woven cloth as in Example 1, a 20% by weight 100% modulus was 90 kg / cm ^2.
An impregnated base material was obtained in the same manner as in Example 1, except that the polyurethane resin solution was impregnated. . The weight ratio of the resin to the fibers in the obtained impregnated base material was 40%.

Production of polishing pad A double-sided pressure-sensitive adhesive tape was laminated on the back surface of the obtained substrate to obtain a polishing pad. The hardness of the surface was 80 °, the water absorption rate was 80 seconds / ml, and the wet strength was 10.0 kg / cm. When the semiconductor wafer was subjected to CMP using the polishing pad, the polishing rate was 0.7 times that of a conventional polishing pad made of foamed hard polyurethane. In addition, in-plane uniformity and step flatness were poor, and the polishing performance inherent in CMP could not be satisfied.

[0027]

According to the present invention, precision polishing for semiconductor wafers, liquid crystal glass, hard disks, etc.,
Having sufficient hardness and wet strength as a polishing pad for MP,
In addition, it is possible to provide an excellent polishing pad capable of easily eliminating clogging by performing simple dressing.

Claims (7)

[Claims] 1. A polishing pad comprising a nonwoven fabric made of non-heat-fused fibers impregnated with a high-molecular elastic polymer, wherein the surface of the polishing pad has a hardness of 85 ° or more and 99 ° or less. Polishing pad. 2. The high-molecular elastic polymer is linear.
100% modulus of 200kgf / cm ² or more 500k
The polishing pad according to claim 1, wherein the polishing pad has a gf / cm ² or less. 3. The non-heat-fused fiber is heated in hot water at 70 ° C. for 30 minutes.
% Or less and 90% or less.
The polishing pad as described. 4. The nonwoven fabric has an apparent density of 0.2 or more.
The polishing pad according to any one of claims 1 to 3, wherein the number is 5 or less. 5. The polishing pad has a water absorption rate of 1 second / ml or more.
The polishing pad according to any one of claims 1 to 4, wherein the polishing rate is 60 seconds / ml. 6. The polishing pad according to claim 1, wherein the polishing pad is for precision polishing. 7. The polishing pad according to claim 1, wherein the precision polishing is for chemical mechanical polishing.